School-age children in Chile received 30 g of wheat-flour biscuits daily through a National School Lunch Program. To improve iron nutrition, these biscuits were fortified with 6% of a bovine hemoglobin concentrate. Hemoglobin iron bioavailability, measured with a double isotope technique, showed that heme-iron absorption in fortified biscuits was high (19.7%). In a pilot field trial, a cohort of 215 school-children received fortified biscuits (30 g) daily during two school periods, and their iron nutrition status was compared with that of children who received non-fortified biscuits (n = 212). Acceptability of both types of biscuits was excellent. Initially, both groups had comparably good iron nutrition. The fortified children presented higher mean ferritin values at the end of the first and second school periods. Good iron stores (serum ferritin greater than or equal to 20 micrograms/lt) were present in 92% and 79% of the fortified and control subjects, respectively (P less than 0.004). The high-iron bioavailability, the good organoleptic characteristics and the biological effect on iron nutriture make this product an appealing alternative to combat iron deficiency.